Aukyixtion  of hydrocarbons



July 4, 1944.

FRACTIONATORS A. R. GOLDSBY ET AL ALKYLATION OF HYDROGARBONS Original Filed June 18, 1938 v CONDENSER EC EIVE R ALKALI INVENTORS ARTHUR R.'GOLDSBY ERNEST r. PEVERE- BY LOUIS A. CLARKE 056E B. ATCH tem and a stream of spent or partially spent sul- 1 Reissued-J uly 4, 1944 ALKYLATION OF HYDROCABBON S Arthur R. Goldsby and Ernest F. Pevere, Beacon,

Louis A. Clarke, Fishfili, and George B. Hatch. Beacon, N. Y., assignors, by mesne assignments, to The Texas N. Y., a corporation oi Company, New York,

Delaware Original No. 2,256,450, dated September 16, 1941, Serial No. 214,488, June 18, 1938. Application for reissue September 24, 1941, Serial No.

7 Claims.

This invention relates to the alkylation of hydrocarbons and has to do with a process for the reaction of certain paraflln hydrocarbons with olefins to produce saturated hydrocarbons of high antiknock value, suitable for the manufacture of motor fuel. I

More particularly the present invention is an improvement in the method for the alkylation of isoparafiins with oleflns in the presence of sulfuric acid as the catalyst. The invention is particularly applicable to the alkylation of lower boiling isoparaflins, such as isobutane and-isopentane, with normally gaseous olefins, including cracking still gases or a fraction thereof such as a fraction containing predominantly C4 hydrocarbons or C; hydrocarbons or a mixture of C: and C4 hydrocarbons; propylene; isomeric normal butenes: isobutylene, or polymers thereof, for example, di-isobutylene and tri-isobutylene: or co-polymers resulting from the polymerization of one molecule of normal butene with one molecuie of isobutylene.

In the alkylationof isoparaflins with oieflns using sulfuric acid as a catalyst, it is customary to contact the mixture 01' olefin and isoparafiin with the acid under such conditions that alkylation of the isoparaflins withv the olefin occurs to produce branch chain, saturated hydrocarbons. In a, continuous type of operation, wherein a stream of hydrocarbons is charged to the sysfuric acid is withdrawn, there may be a substantial amount of oleflns absorbed by the acid and lost or removed from the system with the withdrawn used acid. The loss of olefins in the used acid is particularly observed when the reaction is carried out in a preferred type of continuous multl-stage countercurrent operation wherein the used acid immediately before withdrawal from the system is ordinarily contacted with the fresh hydrocarbon charge'and tends to absorb olefins therefrom.

- In accordance with the present inven ion, the

used acid, before withdrawal from the alkylation.

system, is treated with the isoparaflin to strip the acid of its olefin content.

I additional stages wherein only the isoparaflln,

Although not re- I stricting the invention to any particular theory As applied to a counwhich may be the stream of-isoparaflln charging stock, is contacted with the used acid.

As applied to a countercurrent type of operation using a multiple injection of the olefins between stages in a multi-stage operation, the olefins according to the invention may be injected into the hydrocarbon layer of the settlers, whereby the olefins are mixed with the reaction prod ucts containing a high proportion of isoparaflin to eiiect dilution of the olefins before contacting the mixture with the acid catalyst in a subsequent mixer.

The invention will be mode fully understood from the followingdescription read in connecrelates broadly to the isoparaflin stripping of.

the used acid, is applicable to other systems for carrying out the herein described type of alkylation operation.

Referring to the drawing, the isoparaffin charging stock is introduced by the line I- and pump 2 into a mixer 3 which is provided with a stirring mechanism 5. The charging stock may be mixed with additional isoparamn, recycled in the system through the line 8, as explained more fully hereinafter. In the mixer 3, the isoparaflln is intimately contacted with used acid, which may be spent or partially spent, introduced .through the line 8; The acid may contain a substantial amount. of absorbed olefins and it is intended that the acid be stripped ofthese olefins by con tact with the isoparaflin in the mixer 3. Due to,

' trolled line I 2. The mixer 3 and settler l0 comprise the acid stripping stage, wherein only isoparafilns are contacted with the used acid. While only one stage of acid stripping is shown, it i to be understood that any number may be used:

The hydrocarbons collect in the upper portion of the settler l0 and into this hydrocarbonlayer is introduced a portion-of the olefin chargeby line II which communicates with the olefin portion of the olefin charge may of the settler charging line l containing a pump Ii. By suitable adjustment of the valve II in the line ll, any be introduced into the hydrocarbon layer in the upper portion II. The olefins introduced through the line I commingle with the hydrocarbons in the settler and are. diluted thereby to produce a mixture containing a high proportion of iso-' paraffin to olefins, which is favorable for obtaining the alkylation reaction. Ordinarily the proportion of olefin introduced through the line l5 and the isoparamn introducedthrough the line I, are such as to give an parafiin to olefin of at least 1:1 and preferably from about 3:1 to 5:1. The olefin charge'is ordinarily split between a number of stages, and one skilled in olefin charge to introduce the desired amount into each stage. Ordinarily the proportions introduced in the various stages are about equal and in case the olefin charge is split between three stages, approximately one-third should be introduced through the line ll into the settler II.

The hydrocarbon mixture is transferred from the upper portion of the settler Ill through the line I! to a mixer 20, provided with a stirring mechanism 2]. In the mixer 20, the mixture of iso'paramn and olefins is intimately contacted with partially spent acid introduced into the lower portion of the mixer through the line 22. The reaction products are withdrawn from the mixer through the line 24 and introduced into a overall ratio of isothe art-twill be able to split the settler 25. In this settler the acid and hydrocarbons stratify and the lower acid layer is conducted from the settler through the valve controlled line 8 to the mixer I, referred to heretofore. Into the upper hydrocarbonlayer of the settler 25 is introduced additional olefin through the line Ifwhich communicates with the olefin charging line l5. By suitable regulation of the valve 28 in the line 25, any proportion of the olefin charge. may be commingled with the hydrocarbon layer in the settler 25. 1 r

The hydrocarbon mixture is transferred from the settler I5 through tho-line 29 ton mixer 8|! provided with a stirring mechanism'll. In the mixer ll, the hydrocarbons are contacted .with

sulfuric acid catalyst, comprising partially spent sulfuric acid introduced through the line 33. The reaction mixture is conducted from the mixer II through the line 34 to asettler 35 wherein the separation of acid and hydrocarbon is allowed to take place. The acid layer collecting in the bottom is allowed to flow through the valve controlled line 22 to the mixer 20, referred to herean opportunity for effecting reaction of substantially all the remaining olefin with the isoparaflin. The acid introduced into the mixer is fresh or new acid, which should be about 93 to 100% or more concentration, or preferably about 94 to 98%. This acid, which may be new or restored acid, is introduced through the line by pump 5|. The amount of acid introduced is sufiicient to make the overall ratio of acid to olefin charge about 1:1 or less and preferably about .5 to .8:1. The reaction mixture is transferred from the mixer 48 through the line 53 to a settler 5b. The acid and hydrocarbon separate in the settler 54 and the acid collecting in the lower layer of the settler is conducted through the valve controlled line H to the mixer 40, referred to heretofore. The hydrocarbons are passed from the upper portion of the settler 5i through the line 56 to a mixer 58 provided with a stirrer 59. r

In the mixer 58 the hydrocarbons are intimately contacted with a neutralizing reagent, such as an aqueous alkaline solution, for example dilute caustic solution, introduced through the line 60 by the pump 8|. The mixture of neutralizing reagent and hydrocarbon is passed through the line 63 to a settler 64 wherein the neutralizing reagent settles out and may be withdrawn recycled to the mixer 58 through the branch line 66, which communicates with the line 60. The neutralized hydrocarbons are transferred from the settler 54 through the valve controlled line 61 to fractionator 68. The fractionator' 68 is provided with suitable heating means, such as heating coil 69, whereby substantially all hydrocarbons within the motor fuel boiling range and lower are vaporized and removed overhead throughthe vapor line 10. The bottoms of higher -vapor line HI are introduced into the secondary tofore. Additional olefin is injected into the hydrocarbon layer of settler 15, by means of the line 31 which communicates with the olefin charging line l5, whereby a portion of olefin may be introduced into settler 35 by regulation of the valve 30 in the line 3].

The hydrocarbon mixture is transferred from the settler 35 through the line 3| to a mixer 4! provided with a stirrer ll which intimately mixes the hydrocarbon with the partially spent acid introduced into the mixer through the line 42. The

reaction mixture from the mixer ll is passed through the line 44 to a settler ll wherein the acid separates as a lower layer from the hydrocarbons and is withdrawn-through the valve conboiling point than the desired motor fuel may be withdrawn from the lower portion of the fractionator through the line 12.

The overhead vapors removed through the fractionator or stabilizer 15, wherein a separation is made between the desired motor fuel and lighter hydrocarbons, such as the normally gase ous hydrocarbons. The motor fuel fraction is withdrawn from the lower portion of the frac- -;tionator 15 through the valve controlled line I6.

This motor fuel may be a stable or unstable product falling within the boiling range of gasoline or a normally liquid hydrocarbon fraction of high antiknock value, suitable for blending with gastrolled line SI to the mixer 30, referred to heretofore. The hydrocarbon layer collected in the upper portion of through the line the settler 45 is transferred II to a mixer 5, provided with 15 oline.

The operation of the fractionator 15 may ,vary

considerably, but it is intended to make a sepa- V ration of a fraction relatively rich inisobutane for recycling to the system. If a portion or all of the norm butane is retained in the gasoline which is d, wn from the lowerportion of the fractionator, the remaining products may be fractionated to obtain an isobutane out which may be withdrawn as a side stream through the valve controlled line II, and the lighter hydrocarbons released from the upper portion of the fractionator-through the valve controlled line It. The nature of the products discharged through the line I will, of course, depend some- What on' the character-of the charging stock.

using an isobutane stripping stage in which the For example, if the charging stock is a cracked fraction containing 04 hydrocarbons and lighter, the gases discharged through the line I] may comprise C3 hydrocarbons and lighter. If the charging stock is essentially C4 hydrocarbons, then the overhead product from the fractionator 15 may comprise essentially isobutane, which may be taken overhead through the line 8| instead of the line it. I

In case a portion or all of the normal butane is separated from the gasoline fraction withdrawn from the lower portion of the fractionator 15 through the line 75, then it may be desirable to separate e04 fraction from the fractionator 15 and subject this fraction to further fractionation in another fractionator, not shown, to separate the isobutane from the normal butane. In either case, the isobutane from the line I8 or Ii is passed through a condenser coil 82 wherein it is condensed and the condensate passed through the run-down line 83 to receiver 85. Any portion of the isobutane collecting in the receiver 85 may be passed'through the line 6 containing a pump 86 to the mixer 3, referred to heretofore.

The reaction taking place in the system described is ordinarilyin the liquid phase. Sum-- cient pressure is maintained on the hydrocarbons to maintain them in the liquid phase and this pressure will vary from atmospheric to substantial superatmospheric pressure, depending on the temperatures employed. The temperature may vary from i) to 125 F. or higher, and preferably about 60 to 90 F. 'At these temperatures the pressures may varyfrom to about 10.0 pounds or more, and preferably about 25 to 50 pounds. Suflicient time is provided to obtain substantially complete reaction of the olefins in the alkylation of the isoparafllns. Ordinarily the time would be about to 90 minutes, and preferably to minutes.

As an example of the operation of the invention, the following data were obtained on a fivestage counterfiow apparatus, using as the isoparafiin charging stock a fraction containing about 98% isobutane, and as the olefin charging stock plant gas which was a topped stabilizer reflux containing about 45% C4 olefins, and about 24% isobutane. The isobutane was contacted with the used acid in the first stage and be made without departing from the spirit and spent acid prior to 'withdrawal from the system was contacted with the isobuta-ne charge only,

the yield of 311 end point product was approximately 146%. Also, the recovered acid was of good quality and had a concentration of 94.4%.

The treatment of the used acid with isoparaffin may be used advantageously in connection with any suitable system, including countercurrent or concurrent operation, in which the acid is recycled. In such a case the recycle acid and isoparaflin may be contacted in a separate reactor, for example the initial reactor, and the olefin charged to one or more successive tors.

The present invention has the advantage of I producing increased yields of the desired products and increased acid concentration which permits the use of a smaller fresh acid dosage and longer' use of the acid.

The feature of subjecting a solution of olefin in sulfuric acid to contact with a substantially olefin-free low-boiling isoparafiin to strip absorbed olefin product from the acid, and then passing the resulting mixture of isoparaflin and stripped olefin product to an aikylation reaction zone where the olefin product is alkylated by the isoparaflin in the presence of an alkylation catalyst is disclosed and claimed in copending application, Serial No, 392,874, filed May 10, 1941.

The feature of prediluting the plefin feed to an alkylation reaction zone with separated hydrocarbon phase or alkylate containinga high proportion of isoparaflins prior to contacting the olefin with the alkylation catalyst is disclosed and claimed in copending application, Serial No. 392,396, filed May '1, 1941.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may

scope thereof, and therefore only such limitations should be imposed as are indicated in the apthe plant gas was split and injected into the second and third stages.

Chargeto Stage No. 1 -QIsobutane Charge to stage No. 2 Plant gas Charge to stage No. 3 Plant gas Concentration of sulfuric aid-per cent 98 Acid/olefin ratio 1.18 Isobutane/olefinratio 3.75v Temperature, "F 60.8 Contact time-minutes 90 Percent sulfuric acid in recovered acid 94.4

311-400 F'. fraction:

Percent yield by weight basis of olefin 19.1 Bromine num-ber 1 It will be observed from the above results that 'acid to the alkylation operation.

pended claims.

' We claim:

1. A process for the alkylation of isoparaflins with olefins, which comprises treating olefins and an excess of low boiling isoparaiflns with strong sulfuric acid, whereby the isoparaflins are aikylated by the olefins, separating the used acid from the reaction products. separately contacting at least a portion of the used acid with substantially olefin-free isoparaiilns to strip the acid of absorbed olefins, and passing the mixture of isoparaflins and hydrocarbons stripped from the 2. A process for the alkylation of isoparafiins with olefins. which comprises passing strong sulfuric acid and low boiling isoparaflins serially through a multiple stage reaction zone, intro-" ducing the oleflns inportions into a plurality of said stages, separating the used acid from the reaction products, separately contacting said used acid with substantially olefin-free isoparaffin charging stock to strip the acid of absorbed oleflnic hydrocarbons, and passing the isoparaflln charging stock and hydrocarbons stripped from the acid to the alkylation operation.

3. A process according to claim 2 in which the ficw of the acid and isoparafllns is concurrent.

4. A process according to claim 2 in which the flow of the acid and isoparafflns is countercurrent.

5. In the alkylation of an isoparafiln with an olefin in the presence of concentrated sulfuric acid, the improvement which comprises agitatreac- I ing used alkylation acid with a substantially olefin free isoparaflln to recover absorbed olefin product from the acid to thereby produce an additional quantity of alkylate resulting from the alkylation of the olefin product stripped from the acid by the isoparaflin.

6. In a process for the alkylation of a low-boiling isoparaflin with an olefin, wherein the isoparaflln is contacted with the olefin in the presence of strong sulfuric acid under alkylating conditions in a reaction zone, reaction products are removed to a settling zone where hydrocarbon phase is separated from acid phase. and at least a portion of the separated acid is recycled to the said reaction zone, the improvement which comprises contacting the said recycle acid prior to its return to the said reaction zone with a substantially olefin-free low-boiling lsoparafiin to strip absorbed olefin product therefrom, separating the said isoparafiln with stripped olefin product from the treated acid, and then passing the I treated acid to the alkylation reaction zone.

7. The method according to claim 6, in which the low-boiling isoparaifin which is contacted with the recycle acidis isobutane.

ARTHUR R. GOLDSBY. ERNEST F. FEVER-E. LOUIS A. CLARKE. GEORGE B. HATCH. 

